Time delay mercury switch



March 13, 1934. oos

TIME DELAY MERCURY SWITCH Filed March 25, 1932 2 Sheets-Sheet l ATTORNEYMarch 13, 1934. F. Moos 1,951,162

TIME DELAY MERCURY SWITCH Filed March 25, 1932 2 Sheets-Sheet 2clglVENTOR cf/omZ/ 733001/ C ATTORNEY Patented Mar. 13, 1934 TIME DELAYMERCURY SWITCH Frank Moos, Jersey ility, N. 5., assignor to GeneralElectric Vapor Lamp Company, Hobokcn, N. it, a corporation of New JerseyApplication March 25, 1932, Serial No. 601,232

7 Claims.

The present invention relates to fluid flow switches and particularly toswitches of the time delay type.

The invention consists in a fluid flow switch having the uniqueconstruction and the novel features hereinafter set forth and claimed.

A particular object of the invention is to provide a fluid flow switchin which either the circuit closing or the. circuit opening isaccurately delayed for a predetermined time. Another object of theinvention is to provide a structure for a switch of this type which canbe easily duplicated to give identical time delay periods. Still otherobjects and advantages of the invention will appear from the followingdetailed specification, or from an inspection of the accompanyingdrawings.

Various attempts have been made heretofore to utilize restricted flow ina fluid flow switch to secure a delayed operation of the switch.Difficulty has always been encountered, however, in producing a switchof this type having an exact, predetermined, time delay, especially inswitches having sealed vitreous envelopes in which the variations inphysical dimensions are inevitably large, with the result that it hasbeen impossible heretofore to obtain uniformity in this type of switchby any practicable manufacturing procedure. Hence this type of switchhas never gone into the extensive use that its advantages merit. I havenow discovered that by the use of an inner vessel of a type which can beeasily duplicated a constant and predetermined time delay may beobtained, regardless of reasonable variations in the vitreous envelopeinto which it is sealed. This vessel, according to my novel invention,accurately measures the fluid flow and thus inherently causes thecircuit to be made or broken after the exact time delay desired. Thisstructure is easily reproducible by ordinary manufacturing methods, andhence is extremely inexpensive as well as highly satisfactory. For thepurpose of illustrating my invention I have shown several embodir mentsthereof in the accompanying drawings, in

which Fig. 1 is an elevational view, in part section of a mercury switchof the delayed closing type, showing the mercury in the process ofclosing the circuit therethrough,

Fig. 2 is a similar view of the same switch in the open circuitposition,

Fig. 3 is a sectional view of the same switch taken on the line 3-3 ofFig. 2,

Fig. 4 is an elevational view, in part section,

(01. soc-es) of a mercury switch of the delayed opening type, in thecircuit opening position,

Fig. 5 is a sectional view of a modification of the switch of Fig. 1,

Fig. 6 is asectional view taken on the line 0 6-6 of Fig. 5,

Fig. 7 is a sectional view of another modification of the switch of Fig.1,

Fig. 8 is a sectional view of a modification of the switch of Fig. 4,

Fig. 9 is a sectional view taken on the line 99 of Fig. 8,

Fig. 10 is an elevational view, in part section, of another modificationof the switch of Fig. 1, shown in a circuit closing position, and

Fig. 11 is a similar View of the same switch in an open circuitposition.

In these drawings, with particular reference to Figs. 1-3, my novelswitch has a tubular envelope 1 of any suitable vitreous material suchas lead or lime glass, or a borosilicate glass if a more refractoryenvelope is desired. The inleads 2 and 3, of any suitable metal, aresealed into said envelope 1 through a conventional stem press at one endthereof. The inlead 2 extends along the bottom of said envelope 1, theend thereof being welded to -a metal trough 4 which lies on the bottomof said envelope. Said trough, which may be made of iron, chrome-ironalloy, or other metal which does not readily amalgamate with mercury,has a curvature which is approximately that of the inner wall of theenvelope '1, and a depth which approximates the radius thereof. One endof said trough is closed, this end preferably being close to the end ofsaid envelope which is opposite the stem press, while the other end ofsaid trough is open. A sloping battle 5 which is welded to said troughat a point intermediate the ends thereof to form a vessel ofpredetermined content has a small opening 6 therethrough close to thebottom thereof. Said bafile slopes upwardly away from the closed end ofsaid trough 4 where a delayed circuit closing is desired. The inlead 3extends along the envelope 1 above the trough 4 to a point near theclosed end thereof, and then turns downwardly to a point which isslightly below the level of said closed end when said switch is in thecircuit closing position, as shown in Fig. 1. Said inlead 3 ispreferably coated with glass or other vitreous insulation to a pointnear the bend therein. A quantity of mercury 7 which is sufficient tofill the space behind the baffle 5, but no more, when the switch is inthe circuit opening position shown in Fig. 1, is enclosed within saidenvelope 1. An llO are suppressing atmosphere of hydrogen or the like isalso preferably sealed within said envelope.

In the use and operation of this switch, assuming it to be in the opencircuit position shown in Fig. 2, the switch is abruptly tilted to theposition shown in Fig. 1 in order to close the circuit therethrough. Theentire amount of the mercury 7 is thereupon trapped behind the bafile 5and forced to flow through the restricted opening 6. The mercury flowingthrough this opening forms a pool I which rests against the closed endsof the trough 4, the level of this pool gradually rising until it makescontact with the end of the inlead 3 after a predetermined time of theorder of several seconds, closing the circuit through the switch.Further mercury flow after this is, of course, immaterial aside from itseffeet in lessening the resistance of the circuit through the switch. Solong as the switch is left in this position the circuit therethroughobviously remains closed. Since the mercury pool '7 is thus formedwithin a vessel which may easily be preformed with a constant volume,and since the relation of the inlead 3 with respect to this pool may beeasily adjusted before the stem press carrying the entire inleadassembly is sealed into the envelope 1, it is obvious that the timedelay may be accurately predetermined, regardless of reasonablevariations in the diameter of the envelope 1 or of the position of thetrough 4 therein. As a result switches having this construction may bemanufactured without difiiculty with complete uniformity of the productaresult which has not been heretofore attainable in time delay switcheshaving vitreous envelopes.

To open the circuit through this switch the envelope 1 is abruptlytilted to the position shown in Fig. 2, whereupon the mercury '7 flowsover the sloping baffle 5 without hindrance, opening the circuit throughthe switch instantaneously, and resetting the switch for the delayedclosing operation previously described.

Variations in the time delay of this switch may obviously be produced byvarying the size of the opening 6, by extending the end of the inlead 3(or by moving it nearer to the closed end of the trough 4), by varyingthe depth of the trough 4, or by varying the diameter of trough 4. Allof these variations are easily controlled before the inlead assembly isfused into the envelope 1, so that duplication of the result is easilyattained, whatever time delay is desired.

The switch shown in Fig. 4 is in many respects identical with that shownin Figs. 1-3, the trough 4 being supported in the envelope 1 by theinlead 2 in the same manner as previously described. The sloping baffle5 is reversed, however, to slope upwardly toward the closed end of thetrough 4. The inlead 13 extends above said trough 4 to a point justbeyond the upper end of said baffle 5, and then downwardly toward thebottom of the trough 4, terminating far enough therefrom, however, toavoid any retention of a mercury globule therebetween. Said inlead 13 ispreferably coated from the seal to the point where it bends downward. Aquantity of mercury 7 which is preferably in excess of that which willbe retained behind the bafile 5 when the switch is in the position shownin Fig. 4 is provided within the envelope 1. A suitable arc suppressingatmosphere is also preferably sealed within said envelope.

Assuming the switch of Fig. 4 to be in the closed circuit position, upontilting it to the position shown in Fig. 4 any mercury '7 in excess ofthat which can be retained by the baflie 5 slops over the top of saidbaffle, leaving an accurately measured pool of mercury 17 behind thebaffle. The mercury contained in this pool slowly escapes through theopening 6, lowering the level of said pool until it falls away from theelectrode 13, opening the circuit through the switch after on exactlypredetermined time. The amount of mercury in this switch should besuflicient to form the desired pool 17 and it is also desirable that itshould be sufficient to begin to cover the opening 6 during the circuitopening operation while the pool 17 still has appreciable head, since ithas been found that this makes the continued flow of said pool 17 morecertain, dash lines indicating the preferred final mercury level. Thetime delay period of this switch may obviously be varied at will in thesame manner as in the delayed closing switch previously described.Likewise the delay period may be accurately controlled withoutdifliculty to produce a highly uniform product.

In some cases it is desirable to make and break the circuit betweenfluid pools, in order to avail of the higher current capacity of aswitch having this type of make and break. The switch of Figs.

and 6 shows how the switch of Fig. 1 may be modified to produce thisresult. In this switch the tubular envelope 21 has therein a vitreous orrefractory body 24 which has substantially the same shape as the trough4 of the switches previously described, plus a barrier 28 forming a cup29 at the closed end thereof into which extends inlead 23. A slopingbaIIle 25, having an orifice 26 near the bottom thereof is fixed withinthe body 24 near the open end thereof in any suitable manner. Forexample, this battle may be inserted within a suitable sloping groove inthe body 24, being cemented therein if desired; or as an alternative itmay be made integral with said body. The inlead 22 extends downwardlyinto contact with the bottom of said body 24 at a point between thebaffle 25 and the barrier 28 and serves to fix the position of said bodywithin the envelope 21. Mercury 27 is contained within said envelope 21in an amount similar to that provided in the switch of Fig. 1, plus thatrequired to fill the cup 29. With this construction it is obvious thatthe delay period is fixed by the shape of the vitreous body 24 and bythe size of the orifice 26, and is wholly unaffected by any variationswhich may occur during assembly and fusion of the various parts of theswitch.

In the use and operation of the switch of Figs. 5 and 6, assuming theswitch to be in the open circuit position shown, the switch is tiltedabruptly to a circuit closing position which is similar to that shown inFig. 1. All of the mercury 27 (except that in the cup 29) is thentrapped behind the baffle 25. This mercury slowly flows through theorifice 26 gradually rising about the inlead 22 until after an exactlypredetermined time delay it overflows the barrier 28 and merges with themercury retained in the cup 29 closing the circuit through the switch.Upon returning the switch to the position shown in Fig. 5 the mercury 27passes over the top of the baille 25 without hindrance, causing it toseparate over the barrier 28 from the mercury which is retained by thecup 29, opening the circuit through the switch and resetting for anothercircuit closing after a definite delay period, as hereinbeforedescribed.

A further variation of theswitch of Figs. 1 and 5 is shown in Fig. 7. Inthis switch the trough 34 has a sloping end, in which there is anorifice 36, in place of the open end shown in the previous 100 rid theswitch of Fig. 1.

figures. This trough,-which may be easily drawn from sheet metal, thustakes the place of the combined trough 4 and baffle 5 of the switch ofFig. 1, for example, and offers some economy in the manufacture of theseswitches. A vitreous or refractory cup 39, which may be formed of glass,porcelain, lavite, fused silica, or the like,

is placed within said trough 34 and against the squarely closed endthereof. The inlead 33 extends into said cup 39, and serves to hold boththe trough 34 and said cup in fixed position within said envelope 21.The inlead 32 extends into said trough 34 at a point between the slopingend thereof and the cup 39. The operation of this switch is obviouslyidentical with that of the switch of Fig. 5, and hence will not befurther described.

Figs. 8 and 9 show how the switch of Fig. 4 may likewise be modified togive a mercury-tomercury make and break. In this modification thetubular envelope 41 has the inleads 42 and 43 sealed into one endthereof through a pinch seal. The inlead 42 is welded to a metal trough4 in which there is welded a sloping bafilc 5, as in Fig. 4. The inlead43 extends past said baffle and then curves downwardly into a vitreouscup 49 .which it holds in position within said trough 4.

This cup is made relatively narrow, as shown in Fig. 9, so as to notmaterially interfere with mercury flow thereby. The inlead 43 ispreferably coated from the seal to a point within the cup 49 in order toprevent undesired closings of the circuit through the switch. Mercury47is supplied within the switch envelope, the amount thereof beingsimilar to that employed in the switch of Fig. 4. An inert arcsuppressing atmosphere of hydrogen, ammonia, or the like is preferablyused in this switch, as in each of the switches previously described.

In the operation of the switch shown in Figs. 8 and 9, assuming theswitch to be in the open circuitposition shown in Fig. 8, when theswitch is tilted to the proper angle in the reverse direction themercury flows over the top of the bafile 5 without hindrance and at oncemerges with the mercury pool retained in the cup 49, closing the circuitthrough the switch. Upon returning the switch to the position shown inFig. 8 a measured quantity of the mercury 1 is retained behind thebaflle 5, any excess flowing over the top thereof. This measuredquantity slowly flows through the orifice 6, with a gradual lowering ofthe mercury level about the cup 49 until after an exactly predeterminedinterval the mer cury 4'7 separates over the rim of said cup 49 from themercury pool within said cup, opening the circuit through the switch.Thus the circuit is both made and broken between mercury pools in aswitch which is easily duplicated by ordinary manufacturing methods.

Each of the switches so far described has had an exact time delay ineither the opening or the closing of the circuit, but not both. In somecases it is desirable, however, to delay both the opening and theclosing by exactly timed intervals. My novel structure can also beemployed to produce this result, a switch for this purpose being shownin Figs. 10 and 11. In this switch the sealed tubular envelope 1,containing a suitable arc suppressing atmosphere, has a trough 4 heldtherein by the inlead 2 in the same manner as At a point intermediatethe ends of said trough 4 there is welded a transverse bafile 55, nearthe bottom of which there is a small orifice 56. Mercury 57 is sealedwithin said envelope, said mercury being sufficient in amount toapproximately fill the vessel formed by the baflle 55 and the closed endof said trough 4 when said switch is in the position shown in Fig. 10,or when it is first turned to the position shown in Fig. 11, but nomore, as shown by dash lines in each of these figures. The inlead 53extends above the trough 4, turning downwardly thereinto close to thebafile 55. While the lower end thereof approaches the bottom of saidtrough, it avoids the line of flow of mercury through the orifice 56,either by terminating above said orifice, or through being located atone side thereof. The relative delay periods in closing and opening thecircuit are, of course, determined by the position of said inlead 53with respect to said trough and bailie, the arrangement shown giving themaximum delay for each operation. Movement of said inlead 53 toward theclosed end of said trough 4 will shorten both the delay periods, whilesuch a movement, accompanied by a proportionate shortening of the inleadto keep it at a constant position with respect to the mercury level whenthe switch is in the position shown in Fig. 10 will maintain the closingdelay constant, but will decrease the circuit opening delay. Thusanydesired ratio may be produced, and both delay periods exactlypredetermined, before the assembly is fused into its enclosing envelope,as in each of the switches previously described.

In the operation of this switch, when the envelope l is tilted to theposition shown in Fig. 10 the mercury 57 is all trapped above the baffle55, and slowly flows through the orifice 56 therein, forming a pooltherebelow which gradually increases until it reaches the levelindicated by the dash line and makes contact with the end of the inlead53 after an exactly predetermined time delay, closing the circuitthrough the switch. Upon tilting the switch to the position shown inFig. 11 the mercury 57 is again all trapped behind the balile 55, asindicated by the dash line, and slowly flows through the orifice 56until the level thereof falls below the end of the inlead 53 after anexactly predetermined time, opening the circuit through the switch. Thusboth the opening and the closing of the switch are delayed for an exacttime.

In each of the switches herein described. it is obvious that the timingof the delay periods is entirely determined by the relation of parts ofthe structure which may be adjusted to their final relative positionbefore sealing into the vitreous envelope, and that the delay period isthus independent of any variations which may result from the fusingprocess; or from reasonable variations in the dimensions of the vitreousenvelope. Thus my novel structure completely avoids the defects producedby such uncontrollable variations in the switches of the prior art, andpermits the mass production of mercury switches having a uniform andperfectly controllable time delay.

While I have described my invention by reference to specific examplesthereof, it is obvious that it is not limited thereto, but that variouschanges, omissions, and substitutions, within the scope of the appendedclaims, may be made therein without departing from the spirit thereof.

I claim as my invention:

1. A fluid flow switch of the time delay type comprising a sealedenvelope of vitreous material, inleads sealed thereinto, an electricallyconducting fiuid in said envelope, and a separate vessel within saidenvelope adapted to contain a predetermined quantity of said fluid, oneend of said vessel constituting a baifle to the flow of said fluid alongsaid envelope, said end having an orifice therein to permit restrictedfluid flow therethrough, the remainder of said vessel fitting the wallof said envelope whereby no fluid can be retained therebetween, saidinleads being adapted to cooperate with the fluid within said vessel tocomplete an electrical circuit through said switch.

2. A mercury switch of the time delay type comprising a sealed envelopeof vitreous material, inleads sealed thereinto, mercury in saidenvelope, and a metallic vessel within said envelope, one end of saidvessel constituting a battle to mercury fiow along said envelope, saidend having an orifice near the bottom thereof to permit re strictedmercury flow therethrough, one of said inleads being attached to saidvessel, and another of said inleads terminating within said vessel.

3. A fluid flow switch of the time delay type comprising a sealedenvelope of vitreous material, inleads sealed thereinto, an electricallyconducting fluid in said envelope, and a separate vessel within saidenvelope having a sloping end and adapted to contain a measured quantityof said fluid, said sloping end having an orifice near the bottomthereof to permit restricted fluid flow therethrough, the remainder ofsaid vessel fitting the wall of said envelope whereby no fiuid can beretained therebetween. said fluid connecting said inleads only when itis above a predetermined level in said vessel.

4. A mercury switch of the time delay type comprising a sealed envelopeof vitreous material, inleads sealed thereinto, mercury in saidenvelope, and a separate vessel within said envelope having a slopingend and adapted to contain a measured quantity of said mercury, saidsloping end having an orifice near the bottom thereof to permitrestricted mercury flow therethrough, the

remainder of said vessel fitting said envelope whereby no mercury can beretained therebetween, each of said inleads being adapted to makecontact with mercury retained by said vessel.

5. A mercury switch of the time delay type comprising a sealed envelopeof vitreous material, inleads sealed thereinto, mercury in saidenvelope, a separate vessel within said envelope adaptto contain ameasured quantity of said mercury, one end of said vessel constituting abaflle to mercury flow within said envelope, said end having an orificenear the bottom thereof to permit restricted mercury flow therethrough,and a refractory dividing wall within said vessel to retain a pool ofmercury within said vessel at all operating positions of said switch,one of said inleads extending into said pool.

6. A mercury switch of the time delay type comprising a sealed envelopeof vitreous material, inleads sealed thereinto, mercury in saidenvelope, a metallic vessel within said envelope adapted to contain ameasured quantity of said mercury, one end of said vessel constituting abafile to mercury flow within said envelope, said end having an orificenear the bottom thereof to permit restricted mercury flow therethrough,and a refractory cup within said vessel, one of said inleads terminatingwithin said cup and the other being connected to said vessel.

7. A mercury switch of the time delay type comprising a sealed envelopeof vitreous material, mercury within said envelope, a pair of inleadssealed into said envelope through a common seal, a metallic vesselaffixed to one of said inleads, one end of said vessel constituting abafile to the free flow of said mercury along said envelope, said endhaving an orifice near the bottom thereof to permit restricted mercuryflow therethrough, the other of said inleads terminating at apredetermined point within said vessel.

FRANK MOOS.

